What Causes Coffee to go Bad?

Coffee seldom goes so bad it's undrinkable. Naturally, you or someone you know may have nightmare examples of coffee stored and forgotten in the fridge, only to be unearthed a year later covered in mold.

Those are very extreme examples.

Generally, it's the combination of time and exposure to oxygen that degrades the freshness of coffee beans.

The more time coffee beans are exposed to oxygen, the more quickly and completely they degrade.

Coffee beans contain oils that the roasting process brings to their surfaces. These oils carry most of the fat and flavor. As the oils degrade, your coffee beans lose most of their flavor.

Bland or off-flavor is the most potent side effect of spoiled coffee. Since the experience of flavor concerns your senses of taste and smell, a coffee may taste bland but smell fine and vice versa.

Other times, your coffee beans may have no smell at all. The absence of smell indicates that your coffee beans are no longer fresh. They are still drinkable, and you may choose to grind and brew them anyway.